Dual fuel tank with FASS fuel pump - Chevy and GMC Duramax Diesel Forum
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post #1 of 11 (permalink) Old 05-30-2019, 10:52 AM Thread Starter
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Dual fuel tank with FASS fuel pump

my truck is a custom built western hauler that had a dual external fuel tank. I installed a FASS last year when my injectors went bad. The way I plumped the lines was with a T on the return lines so the over flow would go back into whichever tank I had selected. So my question is to see your ideas as the way I did it didn't work. I think the CP3 and FASS where dead heading against each other and the CP3 wins as it keeps blowing the fuse for the FASS. Guess the fuse had been blown for a year and didn't know till I was changing the filters out and turned it on just run to let it fill up the filters and it never did. I feel like others have had this designed as people with dual in tanks I could see having this problem. Again am wanting to have the FASS overflow going back into the correct tank. I currently don't use the external fuel tank but if I go a long distance I might since diesel here is currently $2.45 at Walmart and other towns/states are higher. Thanks for the ideas I'm advance.

2004 Chevy 3500 LB7 dually 4 wheel drive with Western Hauler Bed.
Purchased Sept 2017.
Already have had to rebuilt complete front suspension
5/23/18: EGR Delete, LDS SAC45s (172K), FASS Fuel Pump, wehrli custom fab y-bridge.

2002 GMC Sierra 5.3L
1995 Harley Sportster
1949 Chevy Truck (in 10000 pieces)
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post #2 of 11 (permalink) Old 05-31-2019, 07:22 PM
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Not sure about the fuse really but if it was me I would of plumed the return line into the tank in the bed, just cause you wouldnt have to cut the filler neck an mess with it, are you sure it’s wired up right? My fass was plug an play an I can clearly hear it turn on when I turn the key

2002 LB7 5 inch exhaust, ppe boost valve, boost/egt/rail pressure gauges, fass 95
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post #3 of 11 (permalink) Old 06-01-2019, 08:21 AM Thread Starter
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Super,

Yes im 99% sure its wired correct as when I don't have the truck running it's running fine. The moment it starts it blows. Mine was also plug and play.

2004 Chevy 3500 LB7 dually 4 wheel drive with Western Hauler Bed.
Purchased Sept 2017.
Already have had to rebuilt complete front suspension
5/23/18: EGR Delete, LDS SAC45s (172K), FASS Fuel Pump, wehrli custom fab y-bridge.

2002 GMC Sierra 5.3L
1995 Harley Sportster
1949 Chevy Truck (in 10000 pieces)
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post #4 of 11 (permalink) Old 06-01-2019, 07:56 PM
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Do you have the double tap fuse for the fass? I’m no expert but to me it seems like you are pulling to much power from the fuse an it’s blowing it?! If that fuse is tied into something else to?

2002 LB7 5 inch exhaust, ppe boost valve, boost/egt/rail pressure gauges, fass 95
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post #5 of 11 (permalink) Old 06-02-2019, 07:13 AM
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Garage
how is your system set up to switch from tank 1 to tank 2?

2006 4wd crew cab dually, box stock, lbz, 3rd owner. acquired to tow 36 ft. 5th wheel. Planning stock output(no tuning) mods.
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post #6 of 11 (permalink) Old 06-02-2019, 03:55 PM
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I don’t have 2 tanks I just have the fass hooked up to my normal fuel tank, I was just trying to shoot some ideas to ya to see if it helped!

2002 LB7 5 inch exhaust, ppe boost valve, boost/egt/rail pressure gauges, fass 95
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post #7 of 11 (permalink) Old 06-02-2019, 07:47 PM Thread Starter
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Thanks for the ideas, work has been crazy and some reason I haven't gotten the notifications sent to my email. Not sure if it's because on my phone I keep this website open in a tab or something else.

As for as your questions yes I am using the fuse tap that they sent in the kit. Just looked at the fuse that is blowing and followed the wiring and the fuse/wire is the wire that is hooked directly from the battery that is giving it the 12volts. It's the little battery box that has the red 12v flap.

Right now the daul system/wiring/motor is removed but how it works is there is a switch western hauler installed inside the truck that goes down to operate a 4 in 2 out pollak motorized fuel selector. Reason I took everything out is my fuel guage wasn't working and the wiring of the fuel selector on the frame rail looked like junk(I'm a little OCD on wiring looking nice and neat) so I wired it all back stock and my fuel guage is now correct.

You mentioned that if it was you, you would plum it into the tank into the bed so I didn't have to cut the filler neck, what'd you have in mind on that?

2004 Chevy 3500 LB7 dually 4 wheel drive with Western Hauler Bed.
Purchased Sept 2017.
Already have had to rebuilt complete front suspension
5/23/18: EGR Delete, LDS SAC45s (172K), FASS Fuel Pump, wehrli custom fab y-bridge.

2002 GMC Sierra 5.3L
1995 Harley Sportster
1949 Chevy Truck (in 10000 pieces)
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post #8 of 11 (permalink) Old 06-03-2019, 02:14 AM
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This may explain it. The Add A Fuse has two slots, a bottom one and a top one when it is plugged in.

Is your Fass fuse (the 3 amp one) in the top or the bottom slot? It should be in the top. The instructions I got from FASS when I installed mine were backwards. I even contacted FASS and they gave me the wrong information.

Again, the FASS 3 amp fuse belongs on the top.

Im also not sure I understand how you have the plumbing. In order to return the recirculated fuel from the FASS to the tank it is coming from you would need three lines coming from and to each tank:
1. Fuel supply
2. Vent
3. Fuel return from Fass (this is done in the filler neck in the FASS instructions)

Do you have all these lines in each tank?

Would it not be easier, now that your main fuel tank gauge is working to simply plumb the Aux tanks into the main tank and transfer the fuel as needed, simplifying the plumbing significantly?

2008 Silverado 2500HD CCSB LTZ Diesel
FASS 95 Lift Pump (with Baldwin filters), Edge Insight CTS Monitor on a Windshield Mount, Nicktane Fuel Filter Adapter w/ CAT 306-9199 UHE tertiary fuel filter, Bilstein 5100 Stock Height, MBRP Downpipe back 4" exhaust with muffler and FTE 30" resonator/muffler, Sinister EGR Delete, Tuned but wont say who did it, Bushwacker Bed Rail Caps, AMP Research Bedstep, Fumoto oil drain valve, Dorman PS Oil cooler, Pioneer AVIC 7200NEX GPS/Stereo, Air Lift LoadLifter 5000 Air Bags.

Last edited by 407driver; 06-03-2019 at 02:20 AM.
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post #9 of 11 (permalink) Old 06-05-2019, 07:58 PM Thread Starter
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407.. thanks for the information.. I read what you wrote but had to end up going to town before I could really look at it. Unfortunately my truck is dead for a while... Transmission exploded and cracked the house all the way around right after it bolts up to the crossmember. I believe it's right before it bolts up to the transfer case... Anyway it's going to be down a while while save up money. I'll readdress this then.

I do believe my 10 amp mini fuse is in the top but it's the bigger 15 amp that keeps blowing. When I get a transmission I'll swap the fuses and see if that helps.

Thanks guys for the help but having to postpone troubleshooting.

2004 Chevy 3500 LB7 dually 4 wheel drive with Western Hauler Bed.
Purchased Sept 2017.
Already have had to rebuilt complete front suspension
5/23/18: EGR Delete, LDS SAC45s (172K), FASS Fuel Pump, wehrli custom fab y-bridge.

2002 GMC Sierra 5.3L
1995 Harley Sportster
1949 Chevy Truck (in 10000 pieces)
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post #10 of 11 (permalink) Old 06-06-2019, 06:29 AM
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I have dual tanks, I have a sump on each tank going to my Airdog.. no issues.

2010 Yukon XL 2500
LMM straight piped
EFI live tuning by ATP
Airdog 4G
Triple pillar gauges
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